Nonstationary Stochastic Seismic Response Analysis for Earth and Rockfill Dams

In this article, the time domain madal analysis technique for evaluating the nonstationary responses of linear systems is combined with the equivalent linearization approach for determining the stationary responses of nonlinear soil structures. A new analysis method is formed and the nonstationary responses of the earth and rockfill dam are calculated. The results from nonstationary analysis are compared with the ones from the stationary computations. The effectiveness of nonstationarity of input and output is investigated and the relevant conclusions are given

Progress on biodegradable films for antibacterial food packaging

The applications of common-used antibacterial agents and biodegradable polymer materials in food packaging were reviewed. The research progress on biobased antibacterial agents (such as chitosan, plant essential oils, plant extracts, bacteriocins) in food packaging films synthesized from biodegradable polymer materials (such as starch and its derivatives, chitosan, cellulose, protein) was summarized. Most of the biodegradable antibacterial films are applied in the packaging of postharvest transportation and storage of fruits and vegetables. This work provides guidance to develop new intelligent food packaging materials featured by degradability, bacteriostasis and environmental protection

Sensitivity of alpine grassland carbon balance to interannual variability in climate and atmospheric CO2 on the Tibetan Plateau during the last century

As the Earth's third pole, the Tibetan Plateau ecosystems are extremely sensitive to climate change. However, the interannual climate sensitivity of the carbon balance of the Tibetan Plateau alpine grassland has not been well quantified under changes in the climate and atmospheric CO2 concentration. Here, we used a process-based biogeochemistry model, CENTURY, to evaluate the sensitivity of the carbon balance to climate change and rising atmospheric CO2 concentration on the Tibetan Plateau grassland during the period 1901-2010. We show that the magnitude of the increase in net primary production (NPP) (0.31 g cm(-2) yr(-1)) was larger than that in heterotrophic respiration (Rh) (0.26 g Cm-2 yr(-1)), and thus indicate that the Tibetan Plateau grassland acted as a net carbon sink of 7.45 Tg C yr(-1) from 1901 to 2010. The spatiotemporal dynamics of carbon fluxes in the Tibetan Plateau grassland were primarily controlled by temperature, and positively correlated with precipitation and elevated CO2 concentration. The temperature sensitivities of NPP (gamma(Temp)(NPP)), Rh (gamma(Temp)(Rh)), and net ecosystem production (NEP, gamma(Temp)(NEP)) during the period 1961-2010 weakened by 16%, 17%, and 15%, respectively, compared with the period 1901-1960. By contrast, the precipitation sensitivities of these variables, i.e., gamma(Prec)(NPP), gamma(Prec)(Rh), and gamma(Prec)(NEP), strengthened by 46%, 67%, and 23%, respectively, from 1961 to 2010 compared with the 1901-1960 period. The continuing increase in atmospheric CO2 concentration tended to enhance the climate sensitivity of the carbon fluxes, by similar to 3% for hemp and 2%-4% for gamma(Prec), as a result of CO2 fertilization and water use efficiency improvement. The climate sensitivity heterogeneity revealed that interannual variation in Rh is more likely to be amplified than NPP or NEP. The findings imply that climate change exerts a strong influence on the carbon dynamics of the alpine ecosystem in the Tibetan Plateau, and this could further modulate the carbon balance depending on the magnitude of different carbon component fluxes. Our study suggests that changes in the climate sensitivity of carbon dynamics should be considered to further quantify the carbon dynamics in this climate-sensitive region

Changes in soil organic carbon in croplands subjected to fertilizer management: a global meta-analysis

Cropland soil organic carbon (SOC) is undergoing substantial alterations due to both environmental and anthropogenic changes. Although numerous case studies have been conducted, there remains a lack of quantification of the consequences of such environmental and anthropogenic changes on the SOC sequestration across global agricultural systems. Here, we conducted a global meta-analysis of SOC changes under different fertilizer managements, namely unbalanced application of chemical fertilizers (UCF), balanced application of chemical fertilizers (CF), chemical fertilizers with straw application (CFS), and chemical fertilizers with manure application (CFM). We show that topsoil organic carbon (C) increased by 0.9 (0.7–1.0, 95% confidence interval (CI)) g kg(−1) (10.0%, relative change, hereafter the same), 1.7 (1.2–2.3) g kg(−1) (15.4%), 2.0 (1.9–2.2) g kg(−1) (19.5%) and 3.5 (3.2–3.8) g kg(−1) (36.2%) under UCF, CF, CFS and CFM, respectively. The C sequestration durations were estimated as 28–73 years under CFS and 26–117 years under CFM but with high variability across climatic regions. At least 2.0 Mg ha(−1) yr(−1) C input is needed to maintain the SOC in ~85% cases. We highlight a great C sequestration potential of applying CF, and adopting CFS and CFM is highly important for either improving or maintaining current SOC stocks across all agro–ecosystems

Modeling soil organic carbon dynamics and their driving factors in the main global cereal cropping systems

Changes in the soil organic carbon (SOC) stock are determined by the balance between the carbon input from organic materials and the output from the decomposition of soil C. The fate of SOC in cropland soils plays a significant role in both sustainable agricultural production and climate change mitigation. The spatiotemporal changes of soil organic carbon in croplands in response to different carbon (C) input management and environmental conditions across the main global cereal systems were studied using a modeling approach. We also identified the key variables that drive SOC changes at a high spatial resolution (0.1 degrees x 0.1 degrees) and over a long timescale (54 years from 1961 to 2014). A widely used soil C turnover model (RothC) and state-of-the-art databases of soil and climate variables were used in the present study. The model simulations suggested that, on a global average, the cropland SOC density increased at annual rates of 0.22, 0.45 and 0.69 Mg C ha(-1) yr(-1) under crop residue retention rates of 30, 60 and 90 %, respectively. Increasing the quantity of C input could enhance soil C sequestration or reduce the rate of soil C loss, depending largely on the local soil and climate conditions. Spatially, under a specific crop residue retention rate, relatively higher soil C sinks were found across the central parts of the USA, western Europe, and the northern regions of China. Relatively smaller soil C sinks occurred in the high-latitude regions of both the Northern and Southern hemispheres, and SOC decreased across the equatorial zones of Asia, Africa and America. We found that SOC change was significantly influenced by the crop residue retention rate (linearly positive) and the edaphic variable of initial SOC content (linearly negative). Temperature had weak negative effects, and precipitation had significantly negative impacts on SOC changes. The results can help guide carbon input management practices to effectively mitigate climate change through soil C sequestration in croplands on a global scale

Projected changes of alpine grassland carbon dynamics in response to climate change and elevated CO2 concentrations under Representative Concentration Pathways (RCP) scenarios.

The Tibetan Plateau is an important component of the global carbon cycle due to the large permafrost carbon pool and its vulnerability to climate warming. The Tibetan Plateau has experienced a noticeable warming over the past few decades and is projected to continue warming in the future. However, the direction and magnitude of carbon fluxes responses to climate change and elevated CO2 concentration under Representative Concentration Pathways (RCP) scenarios in the Tibetan Plateau grassland are poorly known. Here, we used a calibrated and validated biogeochemistry model, CENTURY, to quantify the contributions of climate change and elevated CO2 on the future carbon budget in the alpine grassland under three RCP scenarios. Though the Tibetan Plateau grassland was projected a net carbon sink of 16 ~ 25 Tg C yr-1 in the 21st century, the capacity of carbon sequestration was predicted to decrease gradually because climate-driven increases in heterotrophic respiration (Rh) (with linear slopes 0.49 ~ 1.62 g C m-2 yr-1) was greater than the net primary production (NPP) (0.35 ~ 1.52 g C m-2 yr-1). However, the elevated CO2 contributed more to plant growth (1.9% ~ 7.3%) than decomposition (1.7% ~ 6.1%), which could offset the warming-induced carbon loss. The interannual and decadal-scale dynamics of the carbon fluxes in the alpine grassland were primarily controlled by temperature, while the role of precipitation became increasingly important in modulating carbon cycle. The strengthened correlation between precipitation and carbon budget suggested that further research should consider the performance of precipitation in evaluating carbon dynamics in a warmer climate scenario

Changes in soil organic carbon in croplands subjected to fertilizer management: a global meta-analysis

Cropland soil organic carbon (SOC) is undergoing substantial alterations due to both environmental and anthropogenic changes. Although numerous case studies have been conducted, there remains a lack of quantification of the consequences of such environmental and anthropogenic changes on the SOC sequestration across global agricultural systems. Here, we conducted a global meta-analysis of SOC changes under different fertilizer managements, namely unbalanced application of chemical fertilizers (UCF), balanced application of chemical fertilizers (CF), chemical fertilizers with straw application (CFS), and chemical fertilizers with manure application (CFM). We show that topsoil organic carbon (C) increased by 0.9 (0.7-1.0, 95% confidence interval (CI)) g kg(-1) (10.0%, relative change, hereafter the same), 1.7 (1.2-2.3) g kg(-1) (15.4%), 2.0 (1.9-2.2) g kg(-1) (19.5%) and 3.5 (3.2-3.8) g kg(-1) (36.2%) under UCF, CF, CFS and CFM, respectively. The C sequestration durations were estimated as 28-73 years under CFS and 26-117 years under CFM but with high variability across climatic regions. At least 2.0 Mg ha(-1) yr(-1) C input is needed to maintain the SOC in similar to 85% cases. We highlight a great C sequestration potential of applying CF, and adopting CFS and CFM is highly important for either improving or maintaining current SOC stocks across all agro-ecosystems